Semiconductor technology is generally employed for the manufacture of thin film magnetic heads. Since the invention is directed to a specific portion of the process of thin film head production, it should be understood that the description that follows does not include, for ease of explanation and clarity, the large number of process steps that are typically employed but are not deemed to be necessary for disclosing the invention and which are well known to those skilled in the art. The conventional approach for production of thin film magnetic heads, which comprise thin film transducers disposed on head sliders, employs a wafer or substrate 2 made of a ceramic material, such as titanium carbide for example, as shown in FIGS. 1 to 3. At first, the wafer 2 is polished to provide a smooth surface on which a very thin layer of aluminum oxide is deposited. The insulating aluminum oxide layer is lapped and polished to a specified thickness in order to eliminate defects. A first pole piece P1 of a nickel iron alloy, such as Permalloy, is deposited and the pattern of the P1 pole piece and an adjoining interconnect layer is formed by standard masking and photolithographic processes. The interconnect layer is used to connect a bonding pad to one end of a coil assembly 20 disposed between the P1 pole piece and a second pole piece P2. The P1 pole piece and the interconnect layer are plated to a desired thickness and any undesired nickel alloy material as well as the seed layer used for producing the P1 layer are removed by etching.
After deposition of the P1 pole piece, a thin layer of gap material of aluminum oxide 28 is deposited over the entire surface of the P1 pole piece layer. The oxide layer 28 is processed to pattern the nonmagnetic transducing gap layer that is to be disposed between the P1 and P2 pole pieces. A portion of the oxide layer 28, in the area of the back gap and at a via formed in the interconnect and a via at the bonding pad, is removed by standard masking and etching steps.
An insulation layer 24 is then deposited and its pattern defined to be slightly larger than the pattern of the coil assembly 20 which is to be subsequently deposited. The insulation layer 24 is opened at a via of the interconnect and a via of the back gap closure to allow necessary interconnections. To form the first coil assembly 20, a seed layer of titanium or chromium is deposited and a copper layer is deposited thereover. The pattern of the first coil assembly 20 is then defined by masking and electroplating techniques and the photoresist and seed layer are removed. A second insulation layer 23, second coil assembly 19 and a third insulation layer 21 are deposited and formed in the same manner as the insulation layer 24 and first coil assembly 20. A fourth insulation layer 26 is then fabricated and is made slightly smaller than the first insulation layer 24 so that a gentle slope at the edges of the fourth insulation layer 26 is formed. The fourth insulation layer 26 covers the coil assembly 20 and second coil assembly 19 except at the back gap closure and at a via that allows connection of an end of the coil assembly 20 and second coil assembly 19 to external circuitry.
The upper pole piece P2 is then fabricated with the same nickel iron alloy material as the P1 pole piece and makes contact with the P1 pole piece at an opening 12 formed in the transducing gap layer 28 to establish a magnetic closure. The P2 pole piece is later connected to a bonding pad formed by copper plating using a photoresist process. The copper is plated to a height above the highest point of the magnetic yoke structure. The completed thin film head is then encapsulated with a relatively thick aluminum oxide insulating layer which serves as a protective overcoat.
In the prior art approach to manufacturing thin film magnetic heads, an etching step is required during the formation of the nonmagnetic gap to provide the desired opening 12 for the P2 pole piece that is deposited later. It is known that the aluminum oxide gap material that is deposited varies from system to system and between one production line and another, and accordingly the etch rate of the gap material varies significantly. The etching process must be closely controlled to avoid overetching that can cause etchouts of the pole pieces and of the electrical lapping guides which are formed with the thin film heads.